WO2009063371A1 - Wireless communication module - Google Patents

Wireless communication module Download PDF

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Publication number
WO2009063371A1
WO2009063371A1 PCT/IB2008/054664 IB2008054664W WO2009063371A1 WO 2009063371 A1 WO2009063371 A1 WO 2009063371A1 IB 2008054664 W IB2008054664 W IB 2008054664W WO 2009063371 A1 WO2009063371 A1 WO 2009063371A1
Authority
WO
WIPO (PCT)
Prior art keywords
wireless communication
communication module
fdp
substrate
antenna
Prior art date
Application number
PCT/IB2008/054664
Other languages
French (fr)
Inventor
Manuel E. Alarcon Rivero
Mihai A. T. Sanduleanu
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2009063371A1 publication Critical patent/WO2009063371A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/16—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole
    • H01Q9/26—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole with folded element or elements, the folded parts being spaced apart a small fraction of operating wavelength
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
    • H01Q21/061—Two dimensional planar arrays
    • H01Q21/062—Two dimensional planar arrays using dipole aerials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/16—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole
    • H01Q9/28—Conical, cylindrical, cage, strip, gauze, or like elements having an extended radiating surface; Elements comprising two conical surfaces having collinear axes and adjacent apices and fed by two-conductor transmission lines
    • H01Q9/285—Planar dipole

Definitions

  • the wireless communication module may comprise an antenna that has been formed on a substrate for transmitting, or receiving, a radio frequency signal in a millimeter wavelength band.
  • the radio frequency signal may have a frequency of, for example, 60 GHz.
  • the substrate may be composed of, for example, epoxy and resin (polyp henylene oxide).
  • Other aspects of the invention relate to an apparatus, e.g. a data-handling apparatus, that comprises a wireless communication module, and a substrate that is provided with an antenna.
  • Wireless communication in a millimeter wavelength band around, for example, 60 GHz has several interesting features.
  • a wireless transmission path which extends between a transmitter and a receiver, exhibits a relatively high loss per unit of length in the millimeter wavelength band. This is due to absorption by oxygen and obstructions, such as walls. Although the relatively high loss per unit of length precludes long-range communications in the millimeter wavelength band, there are several advantages associated with this relatively high loss.
  • a wireless communication in the millimeter wavelength band is relatively secure. Since a wall will typically attenuate a radiofrequency signal in this band to relatively large extent, the wireless communication will be difficult to intercept in a room next door. It may even be impossible to intercept the wireless communication in the room next door.
  • This property also allows an extensive frequency reuse on a premise: an individual wireless communication can take place in each room at the same frequency of, for example 60 GHz, without mutual interference.
  • Another interesting feature of wireless communication in the millimeter wavelength band relates to bandwidth. It is typically easier to achieve a relatively large bandwidth of, for example, 1 GHz, in the millimeter wavelength band than in a centimeter wavelength band. This is particularly true for antennas.
  • the millimeter wavelength band particularly suited for short-range wireless communications at high data rates.
  • Such a wireless communication may effectively replace a high-speed data cable having a length in the order of, for example, a few decimeters or a few meters.
  • Another interesting feature of wireless communication in the millimeter wavelength band is that antennas are sufficiently small to be formed on a relatively small substrate.
  • a relatively small substrate may comprise one or more integrated circuits receiver circuits, which may be flip chip mounted, as well as one or more antennas formed by conductive tracks.
  • the millimeter wavelength band offers possibilities for relatively small wireless communication modules that can be easily fitted in a relatively great variety of devices.
  • United States patent number 7 119 745 describes printed antenna devices that can operate at microwave frequencies.
  • an integrated circuit is bonded to the surface of a package substrate that comprises a ground plane.
  • a planar substrate comprises an antenna pattern that is formed on a surface of the planar substrate.
  • the planar substrate is flip-chip bonded to the integrated circuit so that the antenna pattern faces towards the ground plane of the package substrate.
  • the device further comprises a package cover with specific characteristics.
  • the independent claims define various aspects of the invention.
  • the dependent claims define additional features for implementing the invention to advantage.
  • the invention takes the following points into consideration. Wideband communications require wideband antennas. However, antenna architectures that provide a relatively large bandwidth are generally large in size, or may be difficult to manufacture, or both. Existing solutions generally imply a trade-off between size and bandwidth: the larger an antenna architecture is, the larger the bandwidth the antenna architecture should provide. It is therefore generally believed that a larger bandwidth can be obtained only at the expense of a larger size.
  • a wireless communication module comprises an antenna having a radiator element that lies in a plane.
  • the antenna further comprises a circular conductive plate that is substantially parallel to the plane in which the radiator element lies.
  • the circular conductive plate is electrically floating.
  • the circular conductive plate behaves as a resonator that interacts with the radiator element. Accordingly, the circular conductive plate has a resonance frequency, which should be appropriately tuned with respect to the radiator element in order to achieve a bandwidth enlargement. It has been found that an appropriate tuning can be achieved when the circular conductive plate has dimensions that are in the order of those of the radiator element. Accordingly, an antenna in accordance with the invention requires a surface area that is comparable with a conventional antenna, which has a relatively small bandwidth. For those reasons, the invention allows wideband communications at relatively low cost, in particular in the millimeter wavelength range.
  • An implementation of the invention advantageously comprises one or more of following additional features, which are described in separate paragraphs that correspond with individual dependent claims. Each of these additional features contributes to achieving wideband communications at relatively low cost.
  • the antenna has preferably been formed on a substrate.
  • the radiator element and the circular conductive plate are formed in different metal layers of the substrate.
  • the radiator element is preferably a dipole-like element that is formed by a conductive track in a metal layer of the substrate.
  • the radiator element is preferably a folded dipole having a length, which is half a wavelength of interest.
  • the circular conductive plate preferably has a diameter that in a range comprised between 50% and 80% of the length of the folded dipole.
  • the conductive track preferably has two portions that are substantially parallel and that extend from a pair of feeding ends of the folded dipole to a pair of external feeding ends.
  • the external feeding ends can be coupled to a radio frequency circuit via a coupling path that has a given characteristic impedance.
  • the circular conductive plate preferably covers the pair of external feeding ends.
  • the substrate preferably comprises epoxy and polyphenylene oxide resins.
  • FIG. 1 is a block diagram that illustrates a data-handling apparatus, which is provided with a wireless communication module that includes a substrate on which an antenna array has been formed.
  • FIG. 2 is a pictorial diagram that illustrates the antenna array that has been formed on the substrate.
  • FIG. 3 is a pictorial diagram that illustrates an antenna of the antenna array.
  • FIG. 4 is a block diagram that illustrates a transmitter, which can apply a radio frequency signal to the antenna array.
  • FIG. 1 illustrates a personal computer PC that comprises a wireless communication module WCMl.
  • the wireless communication module WCMl allows the personal computer PC to communicate data to a peripheral device PHD in a wireless fashion. Conversely, the wireless communication module WCMl may also allow the personal computer PC to receive data from the peripheral device PHD in a wireless fashion.
  • the peripheral device PHD is also provided with a wireless communication module WCM2, which may be similar to the wireless communication module WCMl in the personal computer PC.
  • a wireless communication between the personal computer PC and the peripheral device PHD may take place in a millimeter frequency band, for example, on a frequency of 60 GHz.
  • the wireless communication module WCMl of the personal computer PC comprises a substrate SUB on which an antenna array AA has been formed.
  • An integrated circuit IC is flip-chip mounted on the substrate SUB.
  • the integrated circuit IC may comprise, for example, a transmitter for applying a radiofrequency signal to the antenna array, or a receiver for processing a radiofrequency signal that the antenna array picks up.
  • the substrate SUB may comprise other electronic components.
  • the substrate SUB may be, for example, a GETEK® laminate composed of composed of epoxy and polyphenylene oxide resins (GETEK® is a registered trademark of GE Electromaterials Corp.).
  • the substrate SUB typically comprises various metal layers in which conductive tracks may be formed. For example, the substrate SUB may comprise four different metal layers.
  • FIG. 2 illustrates the antenna array AA, which has been formed on the substrate SUB.
  • the antenna array AA comprises a total of 40 antennas ANT arranged in the form of four similar rows of 10 antennas.
  • the antennas ANT are identical.
  • An experimental version of the antenna array AA had a length of 2.4 cm and a width of 0.8 cm.
  • the antenna array AA is provided with coupling paths so that each individual antenna is coupled to a transmitter circuit, or a receiver circuit, or both.
  • the coupling paths are arranged so that each individual antenna receives a substantially similar radio frequency signal in terms of phase and amplitude. That is, the antennas are excited with substantially equal amplitudes and phases.
  • the antenna array AA may be shared by a receiver circuit and a transmitter circuit if it is ensured that, at any given time, only one of these circuits operates. This can be achieved by means of time division multiple access (TDMA). Such an operation can be cost- effective because it requires a smaller substrate area to form antennas, compared with a solution wherein one or more antennas are dedicated to reception whereas one or more other antennas are dedicated to transmission.
  • TDMA time division multiple access
  • the antenna array AA allows a relatively high gain in a particular direction, which corresponds to forming a beam. That is, in a transmission mode, the antenna array AA radiates power over relatively small ranges of spherical angles.
  • Computer simulations were carried out for the experimental version of the antenna array AA. The computer simulations revealed an antenna gain of 19.5 decibel (dB) and an efficiency of 82%, which shows that a substantial part of available transmission energy is effectively radiated.
  • FIG. 3 illustrates an antenna ANT of the antenna array AA.
  • the antenna ANT comprises a half wavelength ( 1 AX) folded dipole FDP, which will be referred to hereinafter as folded dipole.
  • a feeding network FN extends from a pair of external feeding ends FEl, FE2 to a pair of internal feeding ends, which belong to the folded dipole FDP.
  • the pair of external feeding ends FEl, FE2 is electrically connected to a coupling path within the antenna array AA mentioned hereinbefore.
  • a circular metal plate CMP which is electrically floating, covers a substantial portion of the folded dipole FDP and the feeding network FN.
  • the circular metal plate CMP extends slightly beyond the pair of external feeding ends FEl, FE2.
  • the folded dipole FDP and the feeding network FN are formed by means of a conductive track in a metal layer of the substrate SUB illustrated in FIG. 2. This metal layer is preferably the top metal layer.
  • a manufacturing process imposes geometrical constraints on the conductive track in terms of minimal width and minimal spacing.
  • the conductive track is 75 micrometers wide, which corresponds with the minimal width for the manufacturing process that was used.
  • the folded dipole FDP is formed around a slot that is 1220 micrometers ( ⁇ m) long and 65 ⁇ m wide. The conductive track surrounds this slot except for a relatively small dipole gap between the internal feeding ends of the folded dipole FDP.
  • the width of the slot which is 65 ⁇ m, corresponds with the minimal spacing for the manufacturing process that was used.
  • the folded dipole FDP has a total length of 1370 ⁇ m, which corresponds to the length of the slot plus two times the width of the conductive track.
  • the feeding network FN comprises two symmetrical portions of the conductive track. These two track portions extend from the pair of external feeding ends FEl , FE2 to the pair of internal feeding points, which belong to the folded dipole FDP. Each track portion is 320 ⁇ m long, which implies a similar distance between the pair of external feeding ends FEl, FE2 and the pair of internal feeding ends. A spacing of 65 ⁇ m exists between the two track portions that belong to the feeding network FN. The spacing thus corresponds with the minimal spacing for the manufacturing process that was used.
  • the circular metal plate CMP is formed in a metal layer that is different from the metal layer in which the folded dipole FDP and the feeding network FN are formed.
  • the folded dipole FDP and the feeding network FN are preferably formed in the top metal layer of the substrate SUB.
  • the circular metal plate CMP may be formed in the metal layer directly beneath the top metal layer or another metal layer.
  • the circular metal plate CMP is electrically floating, which means that this plate is preferably not coupled to signal ground, either directly or indirectly.
  • the antenna ANT illustrated in FIG. 3 basically operates as follows.
  • the folded dipole FDP constitutes a transducer that converts an electrical signal, which is present at the pair of internal feeding ends, into an electromagnetic field, or vice versa, in accordance with a given radiation pattern.
  • the folded dipole FDP has a given impedance at the pair of internal feeding ends, which will be referred to as internal antenna impedance hereinafter.
  • the feeding network FN constitutes an impedance transformer that transforms the internal antenna impedance into an external antenna impedance, which is present at the external feeding ends.
  • the external antenna impedance may be, for example, 50 ohm, which is typical value.
  • the coupling paths of the antenna array AA preferably have the same impedance.
  • the circular metal plate CMP allows the antenna ANT to have a bandwidth that is substantially larger than that of a conventional folded dipole.
  • the circular metal plate CMP has an optimum diameter, which can empirically be established.
  • the optimum diameter was approximately 60% of the total length of the folded dipole FDP. This implies that the optimum diameter was approximately one third of a wavelength (V 3 X) taking into account the dielectric characteristics of the substrate.
  • the circular metal plate CMP also has an optimum location in terms of bandwidth enlargement.
  • Favorable results were obtained with a location as illustrated in FIG. 3, whereby the circular metal plate CMP is substantially centered with respect to the folded dipole FDP and whereby the circular metal plate CMP slightly extends beyond the pair of external feeding ends FEl, FE2.
  • the circular metal plate CMP behaves as a resonator that interacts with the folded dipole FDP.
  • the circular metal plate CMP and the folded dipole FDP have respective resonance frequencies, which should appropriately be tuned with respect to each other in order to achieve a bandwidth enlargement.
  • the diameter of the circular metal plate CMP constitutes one tuning parameter for which an optimum value may empirically be established.
  • the antenna ANT illustrated in FIG. 3 has been a subject of computer simulations. These simulations apply to an implementation on a relatively low-cost substrate composed of epoxy and polyphenylene oxide resins. This substrate is recommended for applications up to 24 GHz, whereas the antenna ANT is designed to operate at frequencies around 60 GHz.
  • the computer simulations provided the following results.
  • the gain of the antenna ANT in so-called odd-mode excitation at 60 GHz is -4.2 dB.
  • the antenna ANT has a -10 dB bandwidth that ranges from 57 GHz to 67 GHz.
  • the antenna ANT has an efficiency of 50%. This is satisfactory for short-range communications or applications where radiated power levels are relatively low, or both.
  • the efficiency can be regarded as relatively high in view of the substrate SUB that is used.
  • FIG. 4 illustrates an implementation of a transmitter circuit TX, which can provide a driving signal for the antenna array AA illustrated in FIG. 2.
  • the transmitter circuit TX comprises a frequency synthesizer FSY that is provided with a crystal resonator XT, a controllable oscillator VCO, and two mixers MIXl, MIX2.
  • the transmitter circuit TX further comprises a baseband and modulation processor BBMP, two controllable amplifiers PAMl, PAM2, and two summing circuits SUMl, SUM2.
  • the transmitter circuit TX basically operates as follows.
  • the frequency synthesizer FSY, the controllable oscillator VCO, and the two mixers MIXl, MIX2 constitute a circuit arrangement that generates two radiofrequency carrier signals IC, QC that have a phase quadrature relationship: an in-phase carrier signal IC and a quadrature carrier signal QC. These carrier signals have a frequency that is determined by the frequency control signal FC, which the transmitter circuit TX receives.
  • controllable oscillator VCO provides a set of four oscillator signals that are phase shifted with respect to each other: a 0 phase oscillator signal, a ⁇ /4 phase oscillator signal, a ⁇ /2 phase oscillator signal, and a 3 ⁇ /4 phase oscillator signal. These four oscillator signals have a frequency that is half the frequency of the aforementioned carrier signals.
  • Mixer MIXl multiplies the 0 phase oscillator signal with the ⁇ /2 phase oscillator signal so as to obtain the in-phase carrier signal IC.
  • Mixer MIX2 multiplies the ⁇ /4 phase oscillator signal with the 3 ⁇ /4 phase oscillator signal so as to obtain the quadrature carrier signal QC.
  • the two mixers MIXl, MIX2 thus effectively behave as frequency doubling circuits.
  • the controllable oscillator VCO applies an auxiliary oscillator signal OS to the frequency synthesizer FSY.
  • the frequency synthesizer FSY applies a tuning signal TS to the controllable oscillator VCO so that the frequency of the set of four oscillator signals is equal to a desired frequency of the radio frequency carrier signals IC, QC divided by two.
  • the frequency synthesizer FSY generates the tuning signal TS on the basis of the crystal resonator XT and the frequency control signal FC.
  • the baseband and modulation processor BBMP generates two amplitude modulation signals IM, QM on the basis of the data DA to be transmitted: an in-phase amplitude modulation signal IM and a quadrature amplitude modulation signal QM.
  • Power amplifier PAMl receives the in-phase amplitude modulation signal IM as a gain control signal.
  • Power amplifier PAM2 receives the quadrature amplitude modulation signal QM as a gain control signal. Accordingly, power amplifier PAMl and power amplifier PAM2 provide an amplitude modulated in-phase carrier signal ICM and an amplitude modulated quadrature carrier signal QCM, respectively.
  • the two amplitude modulation signals IM, QM are so that when the two aforementioned amplitude modulated carrier signals ICM, QCM are summed together, or subtracted from each other, a phase modulated signal is obtained that carries the data DA to be transmitted.
  • Summing circuit SUMl subtracts the amplitude modulated quadrature carrier signal QCM from the amplitude modulated in-phase carrier signal ICM. Accordingly, summing SUMl circuit provides a first antenna ANT driving signal ASl, which has a phase modulation that represents the data DA to be transmitted. Summing circuit SUM2 adds the aforementioned modulated carrier signals ICM, QCM together. Accordingly, summing circuit SUM2 provides a second antenna ANT driving signal AS2, which also has a phase modulation that represents the data DA to be transmitted. CONCLUDING REMARKS
  • the invention may be applied to advantage in any type of product or method that involves a wireless transmission.
  • a wireless communication between two data-handling apparatuses, as illustrated in FIG. 1, is merely an example.
  • the invention may equally be applied to advantage in, for example, imaging applications for medical, security, or industrial purposes.
  • Such an application requires an array of modules provided with an antenna arrangement and a receiver circuit or a transmitter circuit, or both.
  • the array of modules surrounds an object of interest.
  • One of the modules is in a transmitting mode, whereas the other modules are in a receiving mode.
  • the object of interest will cause a back scattering of transmitted energy, which will be received by the modules that are in the receiving mode.
  • An image of the object of interest can be formed on the basis of this received back scattering energy. Appropriate processing is required.
  • the image will have a resolution that depends on parameters such as frequency and bandwidth. These parameters also determine a depth of view, that is, how deep one can view into the object of interest.
  • parameters such as frequency and bandwidth. These parameters also determine a depth of view, that is, how deep one can view into the object of interest.
  • Such an imaging application which is based on an array of modules, can be implemented at relatively low cost.
  • antennas within the modules are relatively well protected against environmental factors, such as, for example, humidity.
  • FIG. 3 illustrates an example in which the antenna comprises a half wavelength folded dipole as a radiator element.
  • Another implementation may comprise a different type of radiator element.
  • the antenna may be formed on numerous different types of substrates.
  • a substrate composed of epoxy and polyphenylene oxide resins is an example, which allows low-cost applications, in particular for consumer products. Professional applications may use another type of substrate, which has a lower degree of signal loss but which is more expensive.

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Abstract

A wireless communication module comprises an antenna (ANT) havinga radiator element (FDP) that lies in a plane. The antenna further comprises a circular conductive plate (CPM) that is substantiallyparallelto the plane in which the radiator element (FDP) lies. The circular conductive plate (CPM) is electrically floating.

Description

WIRELESS COMMUNICATION MODULE
FIELD OF THE INVENTION
An aspect of the invention relates to a wireless communication module. The wireless communication module may comprise an antenna that has been formed on a substrate for transmitting, or receiving, a radio frequency signal in a millimeter wavelength band. The radio frequency signal may have a frequency of, for example, 60 GHz. The substrate may be composed of, for example, epoxy and resin (polyp henylene oxide). Other aspects of the invention relate to an apparatus, e.g. a data-handling apparatus, that comprises a wireless communication module, and a substrate that is provided with an antenna.
BACKGROUND ART
Wireless communication in a millimeter wavelength band around, for example, 60 GHz, has several interesting features. A wireless transmission path, which extends between a transmitter and a receiver, exhibits a relatively high loss per unit of length in the millimeter wavelength band. This is due to absorption by oxygen and obstructions, such as walls. Although the relatively high loss per unit of length precludes long-range communications in the millimeter wavelength band, there are several advantages associated with this relatively high loss.
One advantage is that a wireless communication in the millimeter wavelength band is relatively secure. Since a wall will typically attenuate a radiofrequency signal in this band to relatively large extent, the wireless communication will be difficult to intercept in a room next door. It may even be impossible to intercept the wireless communication in the room next door. This property also allows an extensive frequency reuse on a premise: an individual wireless communication can take place in each room at the same frequency of, for example 60 GHz, without mutual interference. Another interesting feature of wireless communication in the millimeter wavelength band relates to bandwidth. It is typically easier to achieve a relatively large bandwidth of, for example, 1 GHz, in the millimeter wavelength band than in a centimeter wavelength band. This is particularly true for antennas. The aforementioned features make the millimeter wavelength band particularly suited for short-range wireless communications at high data rates. Such a wireless communication may effectively replace a high-speed data cable having a length in the order of, for example, a few decimeters or a few meters. Another interesting feature of wireless communication in the millimeter wavelength band is that antennas are sufficiently small to be formed on a relatively small substrate. Accordingly, a relatively small substrate may comprise one or more integrated circuits receiver circuits, which may be flip chip mounted, as well as one or more antennas formed by conductive tracks. Accordingly, the millimeter wavelength band offers possibilities for relatively small wireless communication modules that can be easily fitted in a relatively great variety of devices.
United States patent number 7 119 745 describes printed antenna devices that can operate at microwave frequencies. In such a device, an integrated circuit is bonded to the surface of a package substrate that comprises a ground plane. A planar substrate comprises an antenna pattern that is formed on a surface of the planar substrate. The planar substrate is flip-chip bonded to the integrated circuit so that the antenna pattern faces towards the ground plane of the package substrate. The device further comprises a package cover with specific characteristics.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a wireless communication module that can provide a relatively large bandwidth at relatively moderate cost, in particular in the millimeter wavelength range. The independent claims define various aspects of the invention. The dependent claims define additional features for implementing the invention to advantage. The invention takes the following points into consideration. Wideband communications require wideband antennas. However, antenna architectures that provide a relatively large bandwidth are generally large in size, or may be difficult to manufacture, or both. Existing solutions generally imply a trade-off between size and bandwidth: the larger an antenna architecture is, the larger the bandwidth the antenna architecture should provide. It is therefore generally believed that a larger bandwidth can be obtained only at the expense of a larger size.
In accordance with the invention, a wireless communication module comprises an antenna having a radiator element that lies in a plane. The antenna further comprises a circular conductive plate that is substantially parallel to the plane in which the radiator element lies. The circular conductive plate is electrically floating.
The circular conductive plate behaves as a resonator that interacts with the radiator element. Accordingly, the circular conductive plate has a resonance frequency, which should be appropriately tuned with respect to the radiator element in order to achieve a bandwidth enlargement. It has been found that an appropriate tuning can be achieved when the circular conductive plate has dimensions that are in the order of those of the radiator element. Accordingly, an antenna in accordance with the invention requires a surface area that is comparable with a conventional antenna, which has a relatively small bandwidth. For those reasons, the invention allows wideband communications at relatively low cost, in particular in the millimeter wavelength range.
An implementation of the invention advantageously comprises one or more of following additional features, which are described in separate paragraphs that correspond with individual dependent claims. Each of these additional features contributes to achieving wideband communications at relatively low cost.
The antenna has preferably been formed on a substrate. The radiator element and the circular conductive plate are formed in different metal layers of the substrate.
The radiator element is preferably a dipole-like element that is formed by a conductive track in a metal layer of the substrate. The radiator element is preferably a folded dipole having a length, which is half a wavelength of interest.
The circular conductive plate preferably has a diameter that in a range comprised between 50% and 80% of the length of the folded dipole.
The conductive track preferably has two portions that are substantially parallel and that extend from a pair of feeding ends of the folded dipole to a pair of external feeding ends. The external feeding ends can be coupled to a radio frequency circuit via a coupling path that has a given characteristic impedance.
The circular conductive plate preferably covers the pair of external feeding ends. The substrate preferably comprises epoxy and polyphenylene oxide resins.
A detailed description, with reference to drawings, illustrates the invention summarized hereinbefore as well as the additional features. BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram that illustrates a data-handling apparatus, which is provided with a wireless communication module that includes a substrate on which an antenna array has been formed. FIG. 2 is a pictorial diagram that illustrates the antenna array that has been formed on the substrate.
FIG. 3 is a pictorial diagram that illustrates an antenna of the antenna array.
FIG. 4 is a block diagram that illustrates a transmitter, which can apply a radio frequency signal to the antenna array.
DETAILED DESCRIPTION
FIG. 1 illustrates a personal computer PC that comprises a wireless communication module WCMl. The wireless communication module WCMl allows the personal computer PC to communicate data to a peripheral device PHD in a wireless fashion. Conversely, the wireless communication module WCMl may also allow the personal computer PC to receive data from the peripheral device PHD in a wireless fashion. The peripheral device PHD is also provided with a wireless communication module WCM2, which may be similar to the wireless communication module WCMl in the personal computer PC. A wireless communication between the personal computer PC and the peripheral device PHD may take place in a millimeter frequency band, for example, on a frequency of 60 GHz.
The wireless communication module WCMl of the personal computer PC comprises a substrate SUB on which an antenna array AA has been formed. An integrated circuit IC is flip-chip mounted on the substrate SUB. The integrated circuit IC may comprise, for example, a transmitter for applying a radiofrequency signal to the antenna array, or a receiver for processing a radiofrequency signal that the antenna array picks up. The substrate SUB may comprise other electronic components. The substrate SUB may be, for example, a GETEK® laminate composed of composed of epoxy and polyphenylene oxide resins (GETEK® is a registered trademark of GE Electromaterials Corp.). The substrate SUB typically comprises various metal layers in which conductive tracks may be formed. For example, the substrate SUB may comprise four different metal layers.
FIG. 2 illustrates the antenna array AA, which has been formed on the substrate SUB. The antenna array AA comprises a total of 40 antennas ANT arranged in the form of four similar rows of 10 antennas. The antennas ANT are identical. An experimental version of the antenna array AA had a length of 2.4 cm and a width of 0.8 cm.
The antenna array AA is provided with coupling paths so that each individual antenna is coupled to a transmitter circuit, or a receiver circuit, or both. The coupling paths are arranged so that each individual antenna receives a substantially similar radio frequency signal in terms of phase and amplitude. That is, the antennas are excited with substantially equal amplitudes and phases.
The antenna array AA may be shared by a receiver circuit and a transmitter circuit if it is ensured that, at any given time, only one of these circuits operates. This can be achieved by means of time division multiple access (TDMA). Such an operation can be cost- effective because it requires a smaller substrate area to form antennas, compared with a solution wherein one or more antennas are dedicated to reception whereas one or more other antennas are dedicated to transmission.
The antenna array AA allows a relatively high gain in a particular direction, which corresponds to forming a beam. That is, in a transmission mode, the antenna array AA radiates power over relatively small ranges of spherical angles. Computer simulations were carried out for the experimental version of the antenna array AA. The computer simulations revealed an antenna gain of 19.5 decibel (dB) and an efficiency of 82%, which shows that a substantial part of available transmission energy is effectively radiated. FIG. 3 illustrates an antenna ANT of the antenna array AA. The antenna ANT comprises a half wavelength (1AX) folded dipole FDP, which will be referred to hereinafter as folded dipole. A feeding network FN extends from a pair of external feeding ends FEl, FE2 to a pair of internal feeding ends, which belong to the folded dipole FDP. The pair of external feeding ends FEl, FE2 is electrically connected to a coupling path within the antenna array AA mentioned hereinbefore. A circular metal plate CMP, which is electrically floating, covers a substantial portion of the folded dipole FDP and the feeding network FN. The circular metal plate CMP extends slightly beyond the pair of external feeding ends FEl, FE2. The folded dipole FDP and the feeding network FN are formed by means of a conductive track in a metal layer of the substrate SUB illustrated in FIG. 2. This metal layer is preferably the top metal layer. A manufacturing process imposes geometrical constraints on the conductive track in terms of minimal width and minimal spacing. The conductive track is 75 micrometers wide, which corresponds with the minimal width for the manufacturing process that was used. The folded dipole FDP is formed around a slot that is 1220 micrometers (μm) long and 65 μm wide. The conductive track surrounds this slot except for a relatively small dipole gap between the internal feeding ends of the folded dipole FDP. The width of the slot, which is 65 μm, corresponds with the minimal spacing for the manufacturing process that was used. The folded dipole FDP has a total length of 1370 μm, which corresponds to the length of the slot plus two times the width of the conductive track.
The feeding network FN comprises two symmetrical portions of the conductive track. These two track portions extend from the pair of external feeding ends FEl , FE2 to the pair of internal feeding points, which belong to the folded dipole FDP. Each track portion is 320 μm long, which implies a similar distance between the pair of external feeding ends FEl, FE2 and the pair of internal feeding ends. A spacing of 65 μm exists between the two track portions that belong to the feeding network FN. The spacing thus corresponds with the minimal spacing for the manufacturing process that was used.
The circular metal plate CMP is formed in a metal layer that is different from the metal layer in which the folded dipole FDP and the feeding network FN are formed. As mentioned hereinbefore, the folded dipole FDP and the feeding network FN are preferably formed in the top metal layer of the substrate SUB. In that case, the circular metal plate CMP may be formed in the metal layer directly beneath the top metal layer or another metal layer. As mentioned hereinbefore, the circular metal plate CMP is electrically floating, which means that this plate is preferably not coupled to signal ground, either directly or indirectly.
The antenna ANT illustrated in FIG. 3 basically operates as follows. The folded dipole FDP constitutes a transducer that converts an electrical signal, which is present at the pair of internal feeding ends, into an electromagnetic field, or vice versa, in accordance with a given radiation pattern. The folded dipole FDP has a given impedance at the pair of internal feeding ends, which will be referred to as internal antenna impedance hereinafter. The feeding network FN constitutes an impedance transformer that transforms the internal antenna impedance into an external antenna impedance, which is present at the external feeding ends. The external antenna impedance may be, for example, 50 ohm, which is typical value. The coupling paths of the antenna array AA preferably have the same impedance. The circular metal plate CMP allows the antenna ANT to have a bandwidth that is substantially larger than that of a conventional folded dipole. In this sense, the circular metal plate CMP has an optimum diameter, which can empirically be established. In experimental version of the antenna ANT, the optimum diameter was approximately 60% of the total length of the folded dipole FDP. This implies that the optimum diameter was approximately one third of a wavelength (V3X) taking into account the dielectric characteristics of the substrate. The circular metal plate CMP also has an optimum location in terms of bandwidth enlargement. Favorable results were obtained with a location as illustrated in FIG. 3, whereby the circular metal plate CMP is substantially centered with respect to the folded dipole FDP and whereby the circular metal plate CMP slightly extends beyond the pair of external feeding ends FEl, FE2.
From an electromagnetic point of view, the circular metal plate CMP behaves as a resonator that interacts with the folded dipole FDP. The circular metal plate CMP and the folded dipole FDP have respective resonance frequencies, which should appropriately be tuned with respect to each other in order to achieve a bandwidth enlargement. The diameter of the circular metal plate CMP constitutes one tuning parameter for which an optimum value may empirically be established.
The antenna ANT illustrated in FIG. 3 has been a subject of computer simulations. These simulations apply to an implementation on a relatively low-cost substrate composed of epoxy and polyphenylene oxide resins. This substrate is recommended for applications up to 24 GHz, whereas the antenna ANT is designed to operate at frequencies around 60 GHz.
The computer simulations provided the following results. The gain of the antenna ANT in so-called odd-mode excitation at 60 GHz is -4.2 dB. The antenna ANT has a -10 dB bandwidth that ranges from 57 GHz to 67 GHz. The antenna ANT has an efficiency of 50%. This is satisfactory for short-range communications or applications where radiated power levels are relatively low, or both. The efficiency can be regarded as relatively high in view of the substrate SUB that is used.
FIG. 4 illustrates an implementation of a transmitter circuit TX, which can provide a driving signal for the antenna array AA illustrated in FIG. 2. The transmitter circuit TX comprises a frequency synthesizer FSY that is provided with a crystal resonator XT, a controllable oscillator VCO, and two mixers MIXl, MIX2. The transmitter circuit TX further comprises a baseband and modulation processor BBMP, two controllable amplifiers PAMl, PAM2, and two summing circuits SUMl, SUM2. The transmitter circuit TX basically operates as follows. The frequency synthesizer FSY, the controllable oscillator VCO, and the two mixers MIXl, MIX2 constitute a circuit arrangement that generates two radiofrequency carrier signals IC, QC that have a phase quadrature relationship: an in-phase carrier signal IC and a quadrature carrier signal QC. These carrier signals have a frequency that is determined by the frequency control signal FC, which the transmitter circuit TX receives.
In more detail, the controllable oscillator VCO provides a set of four oscillator signals that are phase shifted with respect to each other: a 0 phase oscillator signal, a π/4 phase oscillator signal, a π/2 phase oscillator signal, and a 3 π/4 phase oscillator signal. These four oscillator signals have a frequency that is half the frequency of the aforementioned carrier signals. Mixer MIXl multiplies the 0 phase oscillator signal with the π/2 phase oscillator signal so as to obtain the in-phase carrier signal IC. Mixer MIX2 multiplies the π/4 phase oscillator signal with the 3π/4 phase oscillator signal so as to obtain the quadrature carrier signal QC. The two mixers MIXl, MIX2 thus effectively behave as frequency doubling circuits. The controllable oscillator VCO applies an auxiliary oscillator signal OS to the frequency synthesizer FSY. In response, the frequency synthesizer FSY applies a tuning signal TS to the controllable oscillator VCO so that the frequency of the set of four oscillator signals is equal to a desired frequency of the radio frequency carrier signals IC, QC divided by two. The frequency synthesizer FSY generates the tuning signal TS on the basis of the crystal resonator XT and the frequency control signal FC.
The baseband and modulation processor BBMP generates two amplitude modulation signals IM, QM on the basis of the data DA to be transmitted: an in-phase amplitude modulation signal IM and a quadrature amplitude modulation signal QM. Power amplifier PAMl receives the in-phase amplitude modulation signal IM as a gain control signal. Power amplifier PAM2 receives the quadrature amplitude modulation signal QM as a gain control signal. Accordingly, power amplifier PAMl and power amplifier PAM2 provide an amplitude modulated in-phase carrier signal ICM and an amplitude modulated quadrature carrier signal QCM, respectively. The two amplitude modulation signals IM, QM are so that when the two aforementioned amplitude modulated carrier signals ICM, QCM are summed together, or subtracted from each other, a phase modulated signal is obtained that carries the data DA to be transmitted.
Summing circuit SUMl subtracts the amplitude modulated quadrature carrier signal QCM from the amplitude modulated in-phase carrier signal ICM. Accordingly, summing SUMl circuit provides a first antenna ANT driving signal ASl, which has a phase modulation that represents the data DA to be transmitted. Summing circuit SUM2 adds the aforementioned modulated carrier signals ICM, QCM together. Accordingly, summing circuit SUM2 provides a second antenna ANT driving signal AS2, which also has a phase modulation that represents the data DA to be transmitted. CONCLUDING REMARKS
The detailed description hereinbefore with reference to the drawings is merely an illustration of the invention and the additional features, which are defined in the claims. The invention can be implemented in numerous different manners. In order to illustrate this, some alternatives are briefly indicated.
The invention may be applied to advantage in any type of product or method that involves a wireless transmission. A wireless communication between two data-handling apparatuses, as illustrated in FIG. 1, is merely an example. The invention may equally be applied to advantage in, for example, imaging applications for medical, security, or industrial purposes. Such an application requires an array of modules provided with an antenna arrangement and a receiver circuit or a transmitter circuit, or both. The array of modules surrounds an object of interest. One of the modules is in a transmitting mode, whereas the other modules are in a receiving mode. The object of interest will cause a back scattering of transmitted energy, which will be received by the modules that are in the receiving mode. An image of the object of interest can be formed on the basis of this received back scattering energy. Appropriate processing is required. The image will have a resolution that depends on parameters such as frequency and bandwidth. These parameters also determine a depth of view, that is, how deep one can view into the object of interest. Such an imaging application, which is based on an array of modules, can be implemented at relatively low cost. Moreover, antennas within the modules are relatively well protected against environmental factors, such as, for example, humidity.
There are numerous ways of implementing an antenna in accordance with the invention. FIG. 3 illustrates an example in which the antenna comprises a half wavelength folded dipole as a radiator element. Another implementation may comprise a different type of radiator element. The antenna may be formed on numerous different types of substrates. A substrate composed of epoxy and polyphenylene oxide resins is an example, which allows low-cost applications, in particular for consumer products. Professional applications may use another type of substrate, which has a lower degree of signal loss but which is more expensive.
There are numerous ways of implementing functions by means of items of hardware or software, or both. In this respect, the drawings are very diagrammatic, each representing only one possible embodiment of the invention. Thus, although a drawing shows different functions as different blocks, this by no means excludes that a single item of hardware or software carries out several functions. Nor does it exclude that an assembly of items of hardware or software or both carry out a function.
The remarks made herein before demonstrate that the detailed description with reference to the drawings, illustrate rather than limit the invention. There are numerous alternatives, which fall within the scope of the appended claims. Any reference sign in a claim should not be construed as limiting the claim. The word "comprising" does not exclude the presence of other elements or steps than those listed in a claim. The word "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps.

Claims

CLAIMS:
1. A wireless communication module (WCMl) comprising an antenna (ANT) having a radiator element (FDP) that lies in a plane, and a circular conductive plate (CPM) that is substantially parallel to the plane in which the radiator element (FDP) lies, the circular conductive plate (CPM) being electrically floating.
2. A wireless communication module according to claim 1 comprising a substrate (SUB) on which the antenna has been formed, whereby the radiator element (FDP) and the circular conductive plate (CPM) are formed in different metal layers of the substrate (SUB).
3. A wireless communication module according to claim 2, the radiator element (FDP) being a dipole-like element that is formed by a conductive track in a metal layer of the substrate (SUB).
4. A wireless communication module according to claim 3, the radiator element
(FDP) being a folded dipole having a length, which is half a wavelength of interest.
5. A wireless communication module according to claim 4, the circular conductive plate (CPM) having a diameter that in a range comprised between 50% and 80% of the length of the folded dipole (FDP).
6. A wireless communication module according to claim 4, the conductive track having two portions (FN) that are substantially parallel and that extend from a pair of feeding ends of the folded dipole (FDP) to a pair of external feeding ends (FEl, FE2), which can be coupled to a radio frequency circuit via a coupling path that has a given characteristic impedance.
7. A wireless communication module according to claim 6, the circular conductive plate (CMP) covering the pair of external feeding ends (FEl, FE2).
8. A wireless communication module according to claim 2, the substrate (SUB) comprising epoxy and polypheny lene oxide resins.
9. An apparatus that comprises at least one wireless communication module
(WCMl) according to claim 1.
10. An apparatus according to claim 9 comprising an array of wireless communication modules that can be placed around an object of interest, at least one of the wireless communication modules being arranged to operate a transmission mode, whereas other wireless communication modules are arranged to operate in a receiving mode so as to form an image of the object of interest on the basis of back scattered energy.
11. A substrate (SUB) for use in a wireless communication module (WCMl) as claimed in claim 2.
PCT/IB2008/054664 2007-11-13 2008-11-07 Wireless communication module WO2009063371A1 (en)

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CN105990650A (en) * 2015-02-15 2016-10-05 泰科电子(上海)有限公司 Folded dipole antenna, wireless communication module and construction methods of folded dipole antenna and wireless communication module

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